Ci  cular  No.  93,  Revisld. 


United  States  Department  of  Agriftflfrire, 


BUREAU   OK  ENTOMOLOGY 
L.   O.    HOWARD,   Entonvl  ■   ut   Bu 


■f\ 


■ 


THE8PRING  GRAIN-APHIS  OB  NO-t  \  l.l.I.I)  -i.U\  I  -:\  III  (J 

i  i,j,t<  i  ,i  graminum  Bond.  > 

Bj   F.  M.  Wi  Ban  r, 
/»/  *'/,.;  cat  and  Forage-Plant  //'-■■/  Investigate 

Th  ■  early  history  in  America  of  the  spring  grain  aphis  (figs,  l  I  . 
which  has  come  i«»  !>e  generally  known  a-  the  "green  bug,"  \\ ;i-  pub- 
lished in  Circular  No.  s">  of  1 1 1  i  —  Bureau,  and  need  not  be  reproduced 


Dg  grain  minum  i 


here.  Suffice  it  to  say  that  it  is  an  imported  species,  long  known  to  be 
destructive  to  growing  grain  in  Europe,  but  not  known  in  this  country 
prior  to  i^-_>.  and  not  as  a  destructive  insect  until  1890.  The  litera- 
ture relating  to  tlii-.  the  third  and  perhaps  most  destructive  outbreak 
of  tin-  pest,  i-  so  misleading  that  1 1  *  i  —  publication  seems  necessary  in 
order  to  prevent  misapprehension  among  farmers,  and  to  afford  them 
all  possible  helpful  information  in  advance  of  future  similar  out- 
breaks. 

MSTRJB1   HON    IN    I  Hi:   I  MUD  STATES. 

Tin-  bisect   i>  usually  common,  ami  i-  found   from  New  Mexico, 
Colorado,  and  Montana  to  the  Atlantic  coast,  approximately  cover- 
he  area  south  of  latitude  II   ,  excepting  Si  ■    York,  Se 
and  New  England,  ami  east  of  longitude  105°.    Within  tin-  territory 
:t-  area  of  destructive  abundance,  as  well  as  ti  -  at- 

tack during*  any  year,  will  lie  regulated  by  two  factors:  First,  the 
84843    Clr.!  -1 


presence  of  young  growing  wheat,  oats,  barley,  or  rye;  and.  second, 
weather  conditions  favoring  its  rapid  increase  and  unfavorable  for 

the  development  of  its  natural  enemies.     It  will  breed  freely  in  the 
fields  from  an  altitude  of  less  than  20  feet  above  sea  level  on  the  At- 


Fig.   2. — The   spring  grain-aphis  or   "green   bug"    (Toxoptera  graminum):   a,  Wingless 
female;  '/,  larva  :  <■,  pupa.    Much  enlarged.     (From  Pergande.) 

lantic  coast  to  an  elevation  of  nearly  8,000  feet  in  Xew  Mexico,  and 
from  eastern  Washington,  southern  Montana,  northwestern  Minne- 
sota, southern  Wisconsin,  northern  Ohio,  and  southern  Pennsylvania 
southward  to  extreme  southern  South  Carolina,  southern  Texas,  and 


In:    •". — The  spring  grain-aphis  or  "  grecu  bug"    (Toxoptera  graminum)  :  ".  Winged  uii- 
granl  :  b,  antenna  of  same.    ".  Much  enlarged  :  h.  highly  magnified.     I  From  Pi  rgande.) 

Xew  Mexico.  Yet.  with  normal  weather  conditions  during  the  first 
four  or  five  months  of  the  year,  these  facts  signify  absolutely  nothing. 
for  this  insect  will  not  be  abundant  enough  to  attract  any  attention 
by  its  injuries. 

[Cir.  93] 


3 


-,  ,,|     i:,  in  i  imn    01     n  Mi'iKMi  RE    i  BTB1  I   HVE  01    rBREAKS. 

This  insect,  aa  with  other  closelj  allied  species  of  aphides,  repro 
duces  m  two  ways,     A.s  cool  weather  approaches  in  autumn  there 
occur  in  greater  or  less  numbers  both  males  and  females,  the  latter 
depositing  eggs  1 3ee  fig.  I), and  it  is  in  the  egg  state  onl}  that,  under 
,„  rnml  weather  conditions  as  to  temperature,  the  "green  bug  "  p 
the  winter,  and  from  these  eggs  il  originates  in  thespring.     Bui  from 
spring  to  fall  there  are  neither  eggs  nor  males;  all  are  females,  and 
these  give  birth  to  living  young  in  a  series  of  generations.     \\  ith  the 
normal  cold  of  early  winter  these  females  gradually  disappear  and 
the  winter  eggs  remain;  but  if  the  winter  temperature  is  mild,  and 
the  temperature  of  the  following  spring  abnormally  cold,  the  summer 
method  of  reproduction  continues  throughout  the  winter  and  during 
spring.     Endeed,  it  is  not  improbable  that  males  and  egg-laying  fe 
males  may  be  found  in  spring,  especially   in  the  South. 


Ti 


le 


orreen  bug  "  will  breed  freely  in 


-     log  grain-aphis 

iminum  i  :    Egg-laying 

f,  -111:1  greatly 

enlaj  -  '  """"" 

enl 


temperatures  ranging  from  above  100 
to  below  16  F.  As  the  young  mature 
in  eieht  days  and  themselves  begin  to 
give  birth  to  young,  it  will  be  seen  that 
an  exceptionally  mild  winter  foll<  wed 
!>v  an  abnormally  cold  spring  offers 
tln>  lir-t  possible  conditions  for  the 
asive  increase  of  the  pest,  which 
would  ordinarily  begin  breeding  only 
in  spring,  and  from  the  eggs. 

With  excessive  reproduction  and  the 
destruction  or  aging  of  it-  food  plant-. 
this    inseel    develops    a    corresponding 
abundance  of  winged  migrating  females,  which  are  the  means  of  the 
spread  northward  or  outward  from  original  centers. 

The  "green  bug"  in  normal  .war-  that  is,  when  it-  breeding  be- 
gins in  spring  i-  effectively  held  in  check  by  it-  natural  enemies,  and 
notably  by  a  minute,  black,  wasplike  insect,  Lygiphlebus  tritic't 
Ashm.  (see  Bg.  5)  that  deposits  eggs  singly  in  the  "green  bugs,"  the 
grubs  hatching  from  the  eggs  feeding  internally  on  the  bug  and  de- 
stroying  it  (see  Bg.  ''•>.  Other  natural  enemies  are  the  larvse  of  cer- 
tain predaceous  flies,  and  the  larva  and  aduks  of  lady-beetles.  The 
little  wasplike  parasite  first  mentioned,  however,  is  the  one  that  keeps 
the  "green  bug"  in  control  in  normal  year-,  and  in  year-  when  the 
latter  i-  mo-t  abundant  finally  overcomes  it.  a-  was  the  case  in  1907 
in  Kansas,  North  Carolina,  and  other  States  in  the  more  northern 
pari  of  the  range  of  the  pest. 

[Or.  93] 


Unfortunately  this  parasitic  wasp — as  with  the  other  beneficial 
insects — is  active  only  while  the  temperature  is  above  56  I\.  or  at 
least  10    above  that  at  which  the  "green  bug"  breed-  freelv:  and 


Fig.  5. — Lysiphlebua  tritici,  principal  parasite  of  the  spring  grain-aphis:  Adult  female 
and  antenna  of  male,  greatly  enlarged.  Egg  of  Lysiphlebus  tritici  at  right,  highly  mag- 
nified.     (Original,  i 


herein  is  the  whole  secret  of  the  irregular  disastrous  outbreaks  of  the 
"green  bug"  in  grain  fields.     As  accounting  for  the  outbreak  in  the 

year   1907,   the"  "green   bug"   had  had   a 
whole  winter  and  the  following  late  spring 
in  which  to  breed  and  multiply  unmolested, 
and  it  accomplished  its  principal  damage, 
as  in  Texas  and  southern  Oklahoma,  before 
the  weather  was  warm  enough  for  the  para- 
site to  increase  sufficiently  to  overcome  it. 
As  further  illustrative  of  the  important 
bearing  of  weather  conditions,  it  is  found 
that    in    the   case   of   the   three    important 
outbreaks  of  this   insect,  namely,   for  the 
years  1890,  1901.  and  1907.  the  temperature 
for  the  first  five  months  of  each  of  these 
years,  including  the  latter  part   of  winter 
and  spring,  was  above  the  normal  for  the 
winter  months  and  below  the  normal  for  the 
spring  months;  in  other  words,  warm  winters  and  cold,  late  springs. 
The  little  parasitic  wasp  which  is  so  useful  in  the  control  of  this 
pest  is  native  to  this  country,  widely  distributed,  and  every  year  does 
its  work  with  the  "  green  bug"  and  with  other  aphides.     It  is  always 
[Cir.93] 


Fig.  0. — Wingless  female  of 
"  green  bug."  eontaiuing 
larva  of  the  parasite  Ly- 
SzphlebUS    ti:!'.:i       Mile  I    eii^ 

larged.      (Original.) 


present  in  grain  fields,  as  shown  \>\  its  appearance  everj  year,  to  win- 
on  these  pests  whenever  the  weather  conditions  make  il  breeding 
and  multiplication  possible,  and  its  rate  of  breeding  is  so  rapid  i  there 

being  o  general  ion  a  I i  everj  ten  days)  thai  with  a  week  or  two  of 

favorable  weather  il  gains  control  over  it-  host  insects  and  destroys 
them. 

rooo    PLANTS. 

The  spring  grain-aphis  is  essentially  a  leaf-infesting  insect,  rarely 
being  found  on  the  stem.    While  preferring  « « : 1 1  — .  it  w  ill  readilj  attack 

wheat,  rye,  and  barley,  and  ma\  often  be  l I  on  the  underside  of 

the  lower  leaves  of  corn.  Corn  excepted,  its  effecl  on  the  l«;i \ <•-  of 
grain,  when  present  in  large  numbers,  i-  to  cause  the  infested  leaves 
to  change  to  a  red  color,  which  seems  to  be  \ery  characteristic  of 
;optera  and  does  not  follow  attack-  of  other  species  of  aphides 
on  these  grains.  The  insect  has  also  been  found  breeding  upon  ;i 
considerable  number  of  grasses,  any  one  of  which  may  constitute  its 
alternating  food  plant  upon  which  it  may  survive  the  summer  in 
different  portions  of  the  United  States.  It  has  been  found  breeding 
freely  upon  marsh  foxtail  (Alopecurus  geniculatus)  in  Oklahoma 
by  Mr.  W.  J.  Phillip-,  and  by  Mr.  ('.  N.  Ainslie  in  Kansas;  on 
yron  occidentalism  also  in  Oklahoma,  by  Mr.  Phillip-,  and  by 
Mi  E.  <  >.  (i.  Kelly  and  Prof.  C.  P.  Gillette  in  Colorado.  Slender 
wheat-grass  (Agropyron  tenerum)  was  found  moderately  infested 
by  Mr.  Ainslie  at  Las  Vegas,  X.  Mex.  The  species  was  found  breed- 
ing upon  Bromus  at  Washington,  D.  ('..  and  also  upon  Porter's  chess 
(Bromus  porteri)  at  Las  Vegas,  X.  Mex.,  and  on  an  undetermined 
species  of  Bromus  at  Mesilla  Park,  X.  Mex.,  all  by  Mr.  Ainslie. 
The  writer  observed  it  \er\  abundantly  on  orchard  grass  (Dactylis 
glomerate)  in  Indiana  in  1890,  and  again  excessively  abundant  in  a 

Small   i-olated   meadow    of  this  grass  near  Midlothian.   Ya..   in    April. 

1907.  This  meadow  was  located  in  a  region  ncl  adapted  to  the  grow- 
ing of  grain,  and  there  was  no  held  of  growing  wheal  or  oats  within 
.">  miles.  Mr.  Kelly  found  it  in  Montana,  inhabiting  marsh  spike- 
grass  {Distichlis  spicata)  in  such  abundance  as  to  l>e  damaging  this 
grass,  which  in  that  part  of  the  country  i-  known  commonly  as 
••-alt  grass.*1  It  was  found  inhabiting  -lender  wild  rye  (Elymvs 
iatus)  at  Las  Vegas,  X.  Mex.,  by  Mr.  Ainslie.  Mr.  Phillip-  found 
it  attacking  little  barley  (Hordevm  ptisillum)  at  Beloit,  Kan-.,  and 
Kingfisher,  Okla.,  while  the  writer  found  this  to  be  of  frequent 
occurrence  throughout  Kan-a-.  Mr.  Kelly  observed  it  abundant 
on  squirrel-tail  grass  (Hordeum  fubatum)  in  Montana,  while  Mr. 
Ainslie  found  it  moderately  abundant  on  Tfordeum  ca  •  near 

Cimarron.  X.  Mex     Wherever  Kentucky  blue-grass  (Poa  pratensis) 
grows,  the  insect  will  probably  be  found  breeding  upon  it  through- 
ICir  asj 


out  the  entire  summer.  In  fact,  this  has  been  actually  observed  to 
occur  in  the  city  of  Washington.  Mr.  Phillips  has  observed  the 
same  thing  in  Indiana,  and  throughout  the  northern  sections  of  the 
country  where  the  Toxoptera  occur-  it  is  more  likely  to  he  found  on 
this  plant  during  summer  than  upon  grain,  excepting,  perhaps, 
during  seasons  of  excessive  abundance.  Mr.  Ainslie  also  found 
it  moderately  abundant  on  beard-grass  (Polyp&gon  monspeliensis) 
about  Albuquerque,  X.  Mex.  It  has  been  found  breeding  on  yellow 
foxtail  or  pigeon-grass  (Iseophorus  glaucus)  by  Mr.  Phillips  at 
Richmond,  Ind..  and  on  green  stipa  {Stipa  viridula)  at  Las  Vega-. 
X.  Mex..  by  Mr.  Ainslie.  In  the  latter  case  the  grass  was  heavily 
infested.  As  one  or  more  of  these  grasses  will  be  found  to  occur 
in  almost  every  portion  of  the  United  State-,  it  would  appear  that 
the  nonoccurrence  of  Toxoptera  in  any  considerable  section  of  coun- 
try can  not  be  due  to  a  lack  of  uncultivated  food  plants.  Of  food 
plants  other  than  grasses  we  have  only  the  one  observation  made 
by  Mr.  Phillips  at  Kingfisher.  Okla.,  April  23.  1007.  where  a  species 
of  ragweed  growing  up  in  a  badly  damaged  wheat  field  was  quite 
heavily  infested  with  Toxoptera,  at  the  time  breeding  freely  on  this 
plant. 

The  outbreak  on  the  grounds  of  the  Department  of  Agriculture 
was  notable  in  some  respects,  in  that  the  continued  close  cutting  of 
the  blue  grass  supplied  a  continual  fresh,  tender  growth  as  food  for 
the  "green  hug."  thus  preventing  the  development  and  escape  of 
winged  females:  and  especially  is  it  notable  in  view  of  the  total  lack 
of  Lysiphlebus  tritici,  the  most  important  of  the  natural  enemies  of 
this  aphis.  The  only  natural  enemy  found  in  this  case  feeding  upon 
the  ;'  green  bug  "  was  the  diminutive  black  and  yellow  lady-beetle 
(Hyperaspis  undulata  Say),  not  previously  known  in  connection  with 
this  pest. 

When  this  outbreak  became  known  to  Mr.  E.  M.  Byrnes,  superin- 
tendent of  Experimental  Garden-  and  Grounds,  he  at  once  had  the 
entire  infested  block  sprayed  with  a  solution  of  one-half  gill  of  rose- 
leaf  nicotine  to  each  gallon  of  weak  soapsuds.  The  application  was, 
however,  ineffective.  Pour  days  later  a  strip  through  this  plat  was 
thoroughlv  saturated  with  a  strong  solution  of  barnyard  manure, 
made  by  soaking  the  manure  in  water.  While  there  was  no  evidence 
that  this  killed  any  of  the  "green  bugs."  after  nine  days  the  pest  was 
notably  less  on  this  area  than  where  the  application  of  manure 
solution  was  not  mad?. 

A  series  of  experiments  was  then  undertaken  under  the  writer's 
direction  by  Mr.  E.  O.  G*Kelly,  as  follow-: 

Tobacco  dust  wa-  applied  at  rates  of  one-fourth,  one-half,  and  1 
pound   to  each  100  square  feet,  but  after  over  a   week  had  elapsed 

•   [Cir.  93] 


from  the  'hue  of  application  no  effect    was  i"  be  observed  and   n<» 
dead  insects  were  found. 

Kerosene  emulsion  was  applied  ai  s  and  10  per  cent  strength  . 
There  was  pract  icall]  no  difference  in  the  effecl  of  these  two  strengths, 
and  ;ii  the  pnd  of  nine  days  n<>  "  green  bugs  "  were  to  be  found  on  the 
areas  so  treated.     Also  there  was  no  perceivable  injury  to  the  grass. 

Whale-oil  soap  solutions,  varying  in  strength  from  one  fourth  of  o 
pound  to  ■_'  pounds  of  soap  to  each  5  gallons  of  water,  were  applied  to 
similar  areas.  In  this  case  the  stronger  solution  injured  the  grass 
slightly,  1  >i 1 1  not  permanently;  in  the  case  of  the  lesser  strengths  there 
was  no  injury  whatever.  The  .effect  on  the  "  green  bug "  was  tin- 
mimic  in  every  case.  They  were  not  only  literally  exterminated  over 
reas  treated,  but  the  applications  seemed  to  protect  from  a  rein 
testation.  Tn  case  of  even  the  weakest  solution  an  examination,  five 
da]  after  the  application  was  made,  revealed  the  "green  bugs"  in 
myriads  and  In  >eding  freely  on  the  untreated  space,  while  but  8 
inches  away  and  on  the  treated  area  living  bugs  were  scarcely  to  be 
found,  though  the  dead  were  to  be  observed  almost  as  abundantly  as 
were  the  living  on  the  space  untreated.  It  musl  I"1  remembered, 
however,  that  these  experiments  were  carried  out  in  grass  kept  closely 
cropped  by  frequent  use  of  the  lawn  mower,  and  the  results  obtained 
in  no  way  reflect  upon  similar  experiments  carried  out  \<\  Messrs. 
Ainslie  and  Phillips  in  the  grain  fields  of  Oklahoma. 

invasion  of  1907. 

\  1  letter  appreciation  of  the  interrelation  of  the  "green  bug"  and 
its  principal  parasitic  enemy  can  be  conveyed  by  giving  a  chrono- 
logical statement  of  our  investigations  of  the  very  disastrous  inva- 
sion of  the  "  green  bug"  during  the  winter  and  spring  of  L907. 

The  first  rumors  of  injuries  by  this  pesl  came  to  us  early  in  Janu- 
ary from  east-central  Texas,  where  the  "green  bugs"  were  reported 
to  Mr.  W.  1>.  Hunter,  in  charge  of  cotton  boll  weevil  investigations 
of  this  Bureau,  a^  attacking  fall  oats.  During  this  month  in  Texas, 
east  of  a  line  drawn  from  near  Gainesville  through  Abilene  and 
San  Antonio  to  Galveston,  the  temperature  was  9  above  the  normal. 
Within  this  area  was  a  smaller  one.  the  boundaries  of  which  may  be 
indicated  by  a  line  drawn  from  Texarkana  to  Fori  Worth,  Waco, 
and  Joaquin.  Over  this  latter  area  the  temperature  for  the  same 
month  was  12  above  the  normal,  and  within  this  area  the  pesl  began 
its  work  of  desl  met  ion. 

Also,  judging   from  data   received   later,  the  pest   began   to  breed 
rapidly  in  fall-sown  oats  in  southern  South  Carolina,  where  the  tem- 
perature was  from  C>     to  9     ab  >ve  the  normal. 
83] 


8 

During  February  all  over  the  region  west  of  the  Mississippi  River 
and  the  Great  Lakes  the  temperature  was  above  the  normal,  and 
in  the  Carolinas  it  was  only  slightly  below.  During  this  month 
much  damage  seems  to  have  been  done  in  Texas,  and  there  is  every 
probability  that  the  pest  was  breeding  freely  in  the  Carolinas,  though 
it  had  not  yet  been  reported  from  the  latter  State". 

Up  to  this  time  the  outbreak  in  Texas  was  being  investigated  by 
Mr.  E.  C.  Sanborn,  an  agent  of  this  Bureau  detailed  to  the  Texas 
Agricultural  Experiment  Station.  The  first  report  of  the  insect 
outside  of  Texas  was  under  date  of  March  u.  from  Mr.  ('.  TT.  Drake, 
of  Summers,  Ark.,  who  reported  that  "a  -mall  green  hug"  had 
destroyed  the  wheat  in  spots  in  the  fields  in  hi-  locality.  This  lettur. 
received  March  11.  led  to  the  prompt  dispatching  of  Mr.  C.  X. 
Ainslie  for  the  West,  with  full  instructions  to  investigate  the  out- 
break thoroughly,  to  experiment  with  mea>ures  for  destroying  the 
insects  in  the  fields,  especially  over  the  >pot-  where  they  seemed  to 
!>.•  most  abundant,  and  to  determine  what  could  be  accomplished  in 
checking  the  ravage-  of  the  pest  by  the  early  introduction  of  natural 
enemies  into  the  infested  fields.  Arrangement-  were  perfected  with 
Mi-.  W.  D.  Hunter  to  ship  to  Arkansas  living  parasites  (LysiphJebus 
tritici),  which  were  then  abundant  in  Texas,  and  the  -ame  train  l>. 
which  Mr.  Ainslie  reached  Summers  brought  several  hoxes  of  the 
parasites.  These  parasites  were  promptly  placed  in  the  infested 
fields  and  liberated  March  IS.  But  Mr.  Ainslie  found  that  both  the 
lady  heetles  and  the  little  wasplike  parasites  (Lysiphlebus  tritici) 
were  already  present  at  Summer-  and  near-by  points  in  greater  num- 
bers than  could  pos>ibly  have  been  introduced.  The  latter  were 
simply  everywhere,  running  about  over  the  young  grain  plants  and 
placing  their  eggs  in  the  bodies  of  the  "  green  bug-." 

Clearly  the  importation  of  parasite-  would  be  useless  under  these 
conditions,  and  Mr.  Ainslie.  hoping  to  find  a  more  favorable  field  for 
the  introduction  of  parasite-  or  direct  experimental  work  with  rem- 
edies, proceeded,  on  March  23,  for  various  points  in  Oklahoma. 

At  Chandler  and  Guthrie,  March  23  to  2.">.  the  pest  was  very 
abundant,  but  the  conditions  at  these  points  were  again  even  less 
favorable  than  in  Arkansas  for  the  introduction  of  parasites.  For 
example,  on  one  blade  containing  about  150  of  the  "green  bugs  "  Mr. 
Ainslie  counted  25  that  were  parasitized.  lie  then  proceeded  to 
Kingfisher  (March  26)  and  here  found  the  parasites  apparently  less 
plentiful  than  at  the  other  points  visited,  which  were  to  the  eastward. 

Arrangements  had  been  made  with  Mr.  Hunter  to  furnish  parasites 
from  Texas  fields  when  these  were  .called  for.  and  in  response  to  a 
telegraphic  request  he  dispatched  a  quantity  of  material  collected  by 
his  a.ssi.-tants  in  Texas  and  in  southern  Oklahoma.     When  this  was 

[Cir.  93] 


9 

received  and  the  para  ite*  liberated  in  the  infested  fields,  native  para 
sites  were  already   issuing  in  great   numbers.     In  other  words,  the 
parasite  was  already  beginning  unaided  it-  active  work  of  control. 
I'»\    March  27  the  "green  bugs"  developed  winged  adults  in  greal 
numbers,  and  these  seemed  to  drift  northward. 

Mr.  Ain-lie  was  instructed  to  look  for  m  region  t<>  the  northward 
where  the  "  green  bug"  was  just  starting,  and  he  made  his  firsl  stop, 
March  30,  ;ii  Wellington,  Sumner  County,  Kans.,  and  found  the  con 
ditions  there  such  a-  to  oiler  n   favorable  field   for  experimentation 
w  ith  parasites. 

By  April  1  the  fields  about  Wellington  were  generally,  though 
sparsely,  infested  with  the  "green  bug,"  represented  in  many  cases 
l>\  winged  females  thai  had  seemingly  migrated  to  these  fields  and 
were  giving  birth  to  their  young.  Lad}  beetles  were  common,  bul 
none  of  the  Lysiphlebus  was  observed.  After  a  couple  of  days  spent 
in  the  vieinitv  of  Wellington,  Mr.  Am-lie  returned  to  Kingfisher  to 
Becure  parasites  for  introduction  into  southern  Kansas,  l>ut  in  the 
meantime  severe  weather,  accompanied  by  beavj  frosts,  had  pre- 
vailed, and  the  parasites  formerly  abundant  at  Kingfisher  had  I ome 

exceedingly  scarce.  \>\  the  5th,  however,  he  began  again  to  find 
\er\  many  parasitized  "green  bugs,"  and  by  the  7th  the  parasites 
themselves  began  to  appear  again.  A  bushel  of  wheat  plant-,  now 
nearly  covered  with  parasitized  "green  bugs,"  was  collected  at  King- 
fisher and  taken  to  Wellington  April  9.  At  tin-  time  fully  12  per 
cent  of  the  "green  bugs"  at  Wellington  were  already  parasitized, 
while  on  the  li'th  Mr.  Ain-lie  counted  as  many  a-  11  parasitized  in- 
dividual- on  a  single  blade  of  wheat. 

About  the  middle  of  March  an  appeal  came  to  this  Bureau  from 
the  Texas  drain  Dealers'  Ajssociation,  through  their  secretary,  Mr. 
II.  B.  Dorsey,  at  Fori  Worth,  to  investigate  the  "green  bug."  In 
response  to  tin-  appeal  Mr.  W.  .1.  Phillip-,  of  the  Bureau  staff,  was 
dispatched  to  Fort  Worth,  arriving  on  the  27th.  Several  days  -pent 
in  examining  Held-  in  the  vicinity  of  Fort  Worth  demonstrated  that 
the  "green  bug"  had  totally  destroyed  the  grain  in  that  vicinity  and 
disappeared,  and  there  was  no  opportunity  for  experimental  work. 
He  then  went,  by  instruction,  to  Iloliart.  Okla..  and  later  relieved 
Mr.  Ain-lie  at  Kingfisher,  and.  in  response  to  a  telegram  from  Mr. 
Ainslie,  -cut  an  amount  of  parasitized  wheat  from  Kingfisher  to 
Wellington  equal  to  or  larger  than  the  first  shipment. 

All  of  the  material  which  Mr.  Ain-lie  took  with  him  from  Okla- 
homa and  that  supplied  him  by  Mr.  Phillips  was  placed  in  a  single 
wheat  field  near  Wellington.  It  i-  safely  estimated,  from  count-  of 
average  wheat  Made-,  that  upward  of  two  and  one-half  million-  of 
parasites  were  thus  liberated  in  a  single  wheat  Held  on  April  '.'.  and 

mm::     Cir  93     09        .: 


10 

by  this  time  many  were  already  there.  This  introduction  of  para- 
sites was  carried  out  in  order  to  give  a  decisive  test  as  to  whether  it 
was  possible  to  aid  in  protecting  fields  in  this  manner  along  the  ad- 
vance line  of  invasion.  The  weather  was  still  cold,  and  if  the  artifi- 
cial introduction  of  parasites  would,  with  the  return  of  warmer 
weather,  hasten  the  control  of  the  "green  bug,''  the  introduction  of 
such  huge  numbers  would  clearly  demonstrate  this  fact.  And  if 
such  introduction  on  a  large  scale  proved  favorable,  it  would  show 
reasonable  ground  for  the  more  general  introduction  of  parasites  in 
lesser  numbers. 

There  was  a  minor  introduction  of  Lysiphlebus  started  at  McPher- 
son,  Kans.,  April  18,  though  this  parasite  was  already" found  in  the 
fields  in  that  vicinity  at  that  time. 

The  weather  during  the  whole  of  April  was  generally  cold  with,  ae 
on  May  4,  an  occasional  storm  that  is  known  to  have  killed  many  of 
the  parasites,  and  though  there  were  brief  periods  of  warm  weather 
during  which  the  parasites  would  increase  rapidly,  the  Lysiphlebus 
did  not  finally  overcome  the  "green  bug"  in  southern  Kansas  until 
about  the  middle  of  May. 

As  will  be  observed,  this  experiment  was  made  under  weather  con- 
ditions almost  uniformly  unfavorable  to  the  parasite  and  favorable 
to  the  development  of  the  "green  bug."  There  is  no  reason  for 
supposing  that  the  weather  would  affect  the  introduced  parasites 
differently  from  those  already  present  when  the  introduction  was 
made. 

Mr.  Ainslie  remained  in  the  vicinity  of  Wellington,  and  more 
briefly  at  McPherson  and  Sterling,  for  the  purpose  of  watching 
these  experiments,  and  he  was,  moreover,  in  direct  communication 
with  Mr.  Phillips  in  northern  Oklahoma :  and  the  two  were  therefore 
able  to  keep  under  their  observation  a  wide  range  of  country,  thus 
eliminating  the  possibility  of  oversight  or  misconception  on  the  part 
of  either  that  might  otherwise  have  occurred. 

It  was  during  this  period  of  generally  cold  weather  in  late  April 
and  early  May.  interspersed  by  shorter  periods  of  weather  favor- 
able to  the  parasites,  that  the  latter  increased  generally  throughout 
Kansas  and,  judging  from  reports,  also  in  Missouri  and  Colorado. 
It  wanted  only  the  more  extended  warm  spell  that  came  soon  after 
to  enable  them  to  get  the  upper  hand  and  subdue  the  pest,  as  they 
did  throughout  the  southern  Atlantic  coast  section  earlier  in  the 
season. 

The  field  in  which  the  two  and  a  half  million  Lysiphlebus  were 
introduced  and  liberated  on  April  0  did  not,  at  the  time  of  the  over- 
coming of  the  pest  in  this  and  the  adjacent  country  in  May.  indicate 
any  benefit  whatever  above  other  fields,  near  or  remote,  where  no 
[Cir.  it::] 


11 

artificial   introductions   had   been   made.    The   resull   of  the  minor 
experiment  at   McPhereon  was,  as  reported  by  Mr.  Kuan-,  no  more 

fa\  t >r:i  1  >l t*. 

I >i i i-i i iir  the  lasi  two  weeks  of  April  ;i  greal  many  small  lol  of 
parasite:'  were  distributed  over  the  southern  and  central  countii 
Kansas  by  Mr.  S.  J.  Hunter,  of  the  Kansas  State  University.  The 
artificial  sending  out  <>f  these  parasites  bj  Mr.  Hunter  and  the  test 
of  distributing  an  enormous  quantity  in  ;i  single  field,  described 
above,  were  legitimate  experiments,  Imt  the  evidence  showed  \>-v\ 
conclusively  that  they  resulted  in  no  benefit  whatever.  In  other 
words,  as  noted  above,  the  parasites  were  already  infesting  12  per 
cciii  of  iIk  "green  bugs"  at  Wellington,  Kan-..  April  9,  when  the 
artificial  introduction  was  made,  and  •"•"  t"  75  \»i  cent  m  King- 
fisher, Okla.,  at  the  same  date,  and  1 1 n\  were  only  waiting  for 
weather  conditions  i<>  make  it  possible  for  them  to  do  their  work. 
.In-i  as  soon  as  the  favorable  weather  arrived  the  parasites  bred  enor- 
mously and  quickly  overcame  the  "  green  bug."  In  no  case  was  there 
I  field  of  the  hundreds  examined  in  southern  Kansas  where  the  para 
natively  present  did  not  outnumber  by  many  thousands  or  hun- 
dreds of  thousands  any  number  that  could  have  been  introduced 
artificially,  at  a  time  when  weather  conditions  had  become  such  that 
tin-  liberations  could  have  had  any  hen. 'lit.  A-  shown  by  the  careful 
investigations  <d'  the  agents  of  this  Bureau  in  the  field,  and  independ 
ently  of  Prof.  E.  A.  Popenoe,  entomologist  of  the  Kansas  State 
Agricultural  College,  and  his  assistants,  the  parasites  were  equally 
abundant  in  all  fields  in  May.  when  weather  condition-  became  favor- 
able, irrespective  of  whether  distributions  had  been  made  or  not. 

The  weather,  therefore,  i-  the  important  influence.  A-  demon- 
strated by  the  experience  of  this  and  other  year-,  these  parasites, 
always  present  in  limited  numbers,  will  overcome  the  aphis  unaided 
a-  soon  a-  weather  condition-  permit,  and  no  artificial  introduction, 
•rival  or  -mall,  appears  to  hasten  or  increase  their  efficiency. 

The  writer  left  Washington  for  Kansas  May  13  t"  take  personal 
charge  id'  the  held  work  in  relation  to  the  "green  bug"  and  to  make 
a  thorough  survey  of  actual  field  condition-.  The  "green  bug"  at 
this  time  i  May  L5)  had  become  abundanl  in  oat-  a-  far  north  as 
Manhattan,  Kan-.:  but  wherever  present  there  were  numbers  of  para- 
sites al-o  already  in  evidence.  Indeed.  Mr.  Phillip-  found  this 
to  he  true  at  Kearney.  Nebr.,  which  point  he  visited  about  a  week 
later.  In  no  instance  was  a  Held  observed,  either  in  the  vicinity  of 
Manhattan  or.  during  the  next  week  or  ten  day-,  anywhere  in  Kan 
-a-,   where   the   para-ite   was  not    present    wherever  the   "green   bug" 

occurred, 
[di 


12 

A  further  experiment,  this  time  tried  for  the  purpose  of  testing  the 
possibility  of  hastening  the  work  of  the  parasite  during  favorable 
weather  by  large  introductions,  was  carried  out  as  follows:  The  sub- 
jects of  the  experiment  were  two  fields  of  oats,  each  containing  4 
acres.  In  one  of  these  it  was  determined  to  introduce  enormous 
numbers  of  parasites  artificially,  keeping  records  of  this  field  for 
comparison  with  the  other  field  in  which  no  introductions  were  made, 


Fin.  7. — Stalk  of  wheat,  the  loaves  covered  with  dead  "  green  bugs  "  killed  by  the  parasite 
hysiphlebua  tritici.     About  natural  size.      (Original.) 

thus  determining  the  measure  of  benefit,  if  any.  which  resulted  from 
the  artificial  introduction.  Mr.  Ainslie  was  instructed  by  wire  to  ship 
from  "Wellington,  Kans.,  G. bushels  of  the  wheat  plants  that  had  been 
destroyed  by  the  "*  green  bug  **  and  which,  in  <ome  cases,  were  literally 
covered  with  the  parasitized  bodies  of  the  pest,  upward  of  500  having 
been  found  on  a  single  plant.     (See  fig.  7.)     Before  taking  up  the  ex- 

[Cir.  93] 


13 

perinient,  however,  it  was  desirable  to  know  just  what  the  conditions 
were  under  which  it  was  begun.  A-  stated  above,  one  of  these  oat 
fields  was  1 1 —« •*  1  for  the  experiment  <>t'  introducing  para  ite  .  while  1 1 1<- 
other  was  kept  as  a  check.  The  Gelds  were  so  widelj  separated  thai 
the  introductions  could  nol  have  spread  from  one  field  to  the  other. 
Sis  areas  of  i  square  yard  each,  selected  for  i In'  examinations  in  dif 
ferent  parts  of  each  field,  were  gone  over  b)  Mr.  Phillips  and  two  of 
Professor  Popenoe's  assistants.  Examinations  of  both  of  these  fields, 
made  on  Ma\  17  and  Is.  showed  that  the  field  in  which  the  p:i i:i ~ i t < ■- 
Bent  from  Wellington  bj  Mr.  AJnslie  were  to  be  Liberated  contained 
approximately  fifty  millions  of  the  unparasitized  "green  bugs''  :m<l 
approximately  one  and  three  quarter  millions  that  were  undoubtedly 
parasit  ized ;  in  other  words,  approximately  3.5  per  cent  of  the  ''green 
bugs"  were  at  that  time  parasitized.  In  the  check  field  the  parasite*- 
were  even  more  abundant,  about  7.*>  per  cent  being  there  found,  by 
similar  counts,  to  be  parasitized. 
On  May  Is  parasites  from  L2  packages,  each  containing  about  half 

■  bushel  of  wheat  plants,  were  liberated  in  one  of  these  fields.    N«>w. 

■  count  similar  to  thai  made  before  the  parasites  were  introduced 
was  made  on  .May  23,  and  this  showed  thai  the  percentage  of  para- 
sitism in  the  field  in  which  the  experiment  was  carried  out  had  in 
creased  only  to  •">. I  per  cent,  while  in  the  field  in  which  no  parasites 
had  been  liberated  it  was  L9.3  per  cent.  On  Ma\  27  a  similar  count 
Was  made,  when  the  percentage  of  parasitism  in  the  field  where  the 
introduction  was  made  «;h  27.1  per  cent,  while  in  the  check  field  it 
was  ">■_'.'>  per  cent.  Clearly,  under  weather  conditions  favorable  for 
their  development,  an  introduction  of  these  parasites  to  the  extent  of 
million-,  carried  oul  under  field  conditions,  did  not  indicate  enough 
efficiency  to  afford  any  encouragemenl  for  the  use  of  this  measure  in 
the  protection  of  the  grain  fields  of  the  fanner  in  case  of  future 
attack. 

With  all  the  artificial  introductions  of  this  parasite  that  were  made 
in  the  grain  field-  of  Kansas  and  adjacent  States  and  Territories, 
there  i-  no  probability  that  a  single  bushel  of  grain  was  saved  therebj 
or  that  the  United  State-  harvested  one  bushel  more  of  grain  than 
it  would  have  harvested  had  no  introduction-  <<(  parasites  been  made 
or  attempted.  In  substantiation  of  thi-  statement  it  is  interesting 
to  note  the  history  of  the  "green  bug'1  during  1907  throughout 
North  and  South  Carolina,  upward  of  a  thousand  mile-  from  where 
an\  introduction  of  parasites  had  been  attempted,  excepting  two 
that  the  writer  himself  conducted.  A  considerable  amount  of  ma- 
terial was  -cut   from  Winston  Salem.  X.  C.,  «'ti  April  20,  to  B  point 

■  few  miles  west  of  Richmond,  Va..  where  it  was  introduced  into  a 
small  meadow  of  orchard  grass,  with  no  grain   field  within  •">  mile-. 

[Clr.SS] 


14 

I  Jut  even  here  the  effect  was  uncertain,  as  the  writer  had  found  the 
parasite  present  in  tliis  locality  before  the  introduction  was  made. 
In  the  other  case  a  larger  consignment  was  sent  from  the  same  local- 
ity in  North  Carolina  to  Sumter,  S.  C,  to  be  placed  in  a  field  of  oats 
that  the  writer  visited  in  company  with  the  owner  on  the  16th  of 
April,  when  parasites  were  found  in  considerable  numbers.  In  this 
case  the  owner  of  the  field,  writing  under  date  of  June  18  and  report- 
ing on  the  outcome  of  the  experiment,  said: 

I  am  sorry  that  the  information  to  lie  derived  from  our  experiments  with  the 
parasites  is  so  indefinite.  It  just  happened  that  other  conditions  probably  over- 
came the  aphis  before  the  parasites  had  time  to  multiply  sufficiently  t<>  get  in 
their  work.  About  the  time  that  your  box  was  received  weather  conditions 
changed  somewhat  from  cool  to  warmer  weather  and  the  Ihilts  seemed  to  dis- 
appear very  rapidly.  From  the  day  the  bugs  disappeared,  the  oats,  the  only 
grain  grown,  began  to  improve,  and  while  they  will  not  make  a  full  crop  by  any 
means,  they  are  much  better  than  we  anticipated  when  you  were  here. 

This  is.  as  the  writer  personally  observed,  also  the  history  of  the 
disappearance  of  the  pest  in  western  North  Carolina,  where  both  fall 
wheat  and  fall  oats  are  grown  and  where  no  parasites  were  intro- 
duced, but  where  they  were  literally  swarming  on  April  20. 

From  all  of  this  it  would  seem  that  throughout  the  greater  areas 
over  which  this  insect  becomes  injurious  it  has  so  far  been  impos- 
sible to  assist  the  work  in  any  way.  We  have  apparently  been  wholly 
unable  to  aid  the  parasites  in  getting  the  upper  hand.  They  accom- 
plished their  work  earlier  in  the  Carolinas  than  in  the  West,  but 
reference  to  the  records  of  the  Weather  Bureau  will  show  that  the 
weather  conditions  as  regards  temperature  were  precisely  such  as  to 
bring  this  about. 

The  only  possibility  of  accomplishing  anything  by  the  artificial 
use  of  natural  enemies  of  the  "green  bug"  seems  to  be  in  Texas  and 
South  Carolina,  where  the  pest  get-  it-  -tart  earliest,  making  its  ap- 
pearance in  the  fields  in  spot-  of  greater  or  less  area  in  the  fall  or 
early  winter.  If  these  incipient  outbreak-  can  be  stamped  out  by 
farm  methods,  as  indicated  further  on.  or  by  the  encouragement  of 
parasites,  or  if  they  can  be  so  weakened  as  to  prevent  the  "  green  bug  " 
from  developing  in*  such  enormous  numbers,  it  will  serve  to  protect 
the  grain  crop-  not  only  of  these  two  State-,  but  of  all  those  to  the 
northward  over  which  the  pest  ravages  in  seasons  favorable  for  its 
development.  The  Texas  Agricultural  Experiment  Station  is  con- 
templating an  experiment  whereby  they  hope,  by  the  artificial  intro- 
duction at  the  proper  time  of  a  large  number  of  the  natural  enemies 
of  the  "  green  bug  "  into  these  spots  of  early  infestation,  to  forestall 
a  future  outbreak.  If  this  can  be  accomplished  it  will  prove  of  great 
benefit  to  the  farmers.  Whatever  the  outcome  may  be,  the  experi- 
ment seems  worth  trying. 
[Cir 


L5 

DEVELOPMENT    \  \i>    I  \  I  1  i  I  \ LYSIPHLEBUS    1 1:1  I  n  I. 

Although  there  are  seyeral  natural  enemies  of  the  "green  bug," 
including  one  recently  described  l»\  Dr.  L.  O.  Howard  aa  Aphelinua 
nigrituH,  \ ft  ;ill  of  them  seem  to  be  of  little  importance  as  compared 
with  the  one  minute  parasitic  species,  Lysiphlebus  tiit',,1.  It  is  this 
species,  or  what  we  are  at  present  terming  as  snch,  that  normally 
holds  Toxoptern  in  check  in  this  country,  and  so  long  as  it-  develop 
men!  and  activity  arc  not  obstructed  bj  adverse  meteorological  condi- 
tions it  will  probably  continue  to  control  it.  Indeed,  so  important  is 
this  insect  and  so  powerful  is  it-  influence  that  in  i  short  space  of 
from  ten  days  to  two  weeks  it  can  overcome  a  most  serious  outbreak  of 
Toxoptera,  and  thus  save  from  destruction  vast  areas  of  growing 
grain.  The  species  winters  over  in  the  field  in  the  body  of  its  host. 
In  many  cases  these  parasites,  having  been  prevented  from  emerging 
the  previous  fall  In  the  advenl  of  cold  weather,  hibernate  as  nearly 
developed  or  fully  developed  adult-,  ready  to  emerge  when  the  tem- 
perature rises  to  about  56  F.  and  remain-  there  for  a  sufficient 
length  of  time.  This  is  clearly  shown  by  the  fact  that  Mr.  E.  < ).  (>. 
Kelly  found  hibernating  adult-  at  Leavenworth,  Kan-.,  on  November 
13.  In  <»ne  lot  of  50  dead,  parasitized  Toxoptera  that  had  been 
washed  or  rubbed  from  the  leaves  of  the  young  grain  and  taken  from 
the  mud  about  the  wheat  plant-  on  February  28,  after  the  winter  was 
practically  over.  Mr.  Kelh  found  17  containing  full-grown  larvae  of 
the  parasite,  12  containing  pupa'  of  a  light  color,  and  21  containing 
dark-colored  pupa',  the  latter  evidently  ready  to  develop  promptly 
with  the  advent  of  warm  weather.  Mi.  Kelly,  on  the  same  date,  also 
secured  a  large  number  of  Toxoptera  in  various  stages  of  development 
that  were  hibernating  in  wheat  fields  near  Leavenworth,  Kan-.  The 
weather  had  been  such  a-  to  preclude  the  possibility  that  these  had 
been  recently  parasitized.  Yet  some  of  them  soon  began  to  -how  the 
yellowish  color  characteristic  of  Toxoptera  parasitized  by  Lysiphle- 
bus,  and  adult-  were  afterwards  reared  from  them.  This  -how-  con- 
clusively that  the  Lysiphlebus  parasites  hibernate  in  advanced  -t.i_ 
of  development  in  the  bodies  of  their  host,  which  they  have  killed  the 
previous  autumn,  and  also  as  larvae  in  those  passing  the  winter  from 
half  to  fully  grown. 

The  female  Lysiphlebus  i-  even  more  prolific  than  the  female 
Toxoptera.  Mr.  Phillip-  has  found  female-  which  had  upward  of 
MX)  eggs  iii  their  ovaries,  and  Mr.  Kelly  has  reared  in  some  cas 
206  individuals  from  a  single  mother  Lysiphlebus.  The  eggs  are 
lemon-shaped  and  white.  When  excessively  abundant  this  parasite 
will  thrust  it-  ovipositor  into  old  and  young  aphides  of  both  sexes, 
including  the  sexual  female  even  though  previously  parasitized;  and 
Mi.  Phillip-  has  observed  that  it  will  even  ovipo-it  in  the  dead  bodies 

[fir.  93] 


16 

of  those  that  have  been  killed  by  fungous  attack.  When  its  numbers 
are  not  so  great  it  shows  more  discrimination  and  seems  to  prefer 
half-grown  individuals  for  oviposit  ion. 

This  species  of  Lysiphlebus  is  parthenogenetic,  as  was  first  ob- 
served  by  Mr.  Phillips  at  Richmond,  Lad.,  and  afterwards  more  fully 
elucidated  by  Messrs.  E".  ().  (i.  Kelly  and  T.  D.  Urbahns  at  Welling- 
ton. Kans.  The  experimental  breedings  by  Mr.  Phillips  in  ]!»07 
indicated  that  the  offspring  of  virgin  female  Lysiphlebus  were  nearly 
always  exclusively  males.  Tn  a  series  of  upward  of  80  breeding 
experiments  carried  on  indoors,  in  1908,  by  Kelly  and  Urbahns,  only 
48  gave  results  of  an}'  kind.  In  only  four  of  these  were  females  pro- 
duced, the  other-  giving  exclusively  males.  In  the  4  exceptional  ca-''- 
the  females  remained  virgin,  and  all  finally  gave  birth  to  males  alone. 
2  with  the  first  generation.  1  with  the  >econd,  and  1  with  the  third. 
The  mode  of  procedure  was  as  follows: 

Starting  with  a  mated  female,  the  females  from  among  her  off- 
spring were  isolated,  even  before  emergence.  On  their  appearance 
these  were  given  Toxoptera  reared  under  cover  to  preclude  parasit- 
ism; the  few  females  from  among  the  second  generation  were  again 
isolated  in  the  same  manner,  the  females  in  all  cases  being  kept  un- 
mated.  It  was  thus  found  possible  to  breed  a  limited  number  of 
females  parthenogenetically  to  and  including  the  third  generation. 
Beyond  this  all  offspring  were  males,  this  seemingly  being  the  limit. 
Just  why  such  a  large  percentage  of  these  experiments  should  have 
proved  abortive  is  not  clear.  The  conditions  under  which  they  were 
carried  out  were  of  course  unnatural  but  much  more  protected  from 
the  adverse  elements  of  the  open  field. 

The  e<ji<<[  of  the  Lysiphlebus  normally  develops  to  the  emerging 
adult  in  about  ten  days,  during  the  first  six  of  which  the  host  insert 
remain-  alive,  and  at  the  end  of  which  it  commences  to  take  on  a 
yellowish  hue.  the  larva  of  the  parasite  showing  clearly  through  the 
skin  of  the  abdomen. 

The  celerity  with  which  an  invasion  of  Toxoptera  is  overcome  by 
Lysiphlebus  is  frequently  a  matter  of  wonder,  as  it  hardly  seems 
possible  that  this  host  alone  could  be  the  source  of  the  swarms  of 
parasites  that  make  their  appearance  after  a  few  warm  days  have 
elapsed  in  the  midst  of  an  unseasonably  cool  spring  preceded  by  a 
winter  abnormally  mild. 

In  order  to  determine  the  origin  of  these  myriads  of  parasites 
Messrs.  Kelly  and  Urbahns  began  a  long  -cries  of  experiment-  at 
Wellington,  Kans..  to  determine  whether  there  might  not  be  a  mul- 
tiplicity of  host  species  from  which  great  numbers  of  Lysiphlebus 
would  emanate  to  fall  upon  and  destroy  Toxoptera  whenever  it  be- 
comes excessively  abundant.     The  entire  failure  to  introduce  tin-' 

[Cir.  93] 


i: 


parasites   in   advance  of  an    invasion   of  this  character    from   the 
ith.  as  was  the  case  ii    Kansas  in   May,  1907,  has  indicated  thai 
such  introductions  were  not  possible  and  thai  to  attempt  it  was  veri- 
tably  "  carrying  coals  to  Newcastle." 

Female  individuals  of  Lysiphlebus  from  the  cabbage  aphis  (Aphis 
braMxicn  L.)  taken  in  the  field  were  firsl  allowed  to  parasitize  Toxop- 
tera  and  from  the  latter  the  adults  were  obtained.  This  experimenl 
w:i-  several  times  repeated.  Females  of  Lysiphlebus  reared  under 
cover  from  the  corn  root-aphis  {Aphis  maidi-radiris  Forbes)  were  in 
two  cases  allowed  to  parasitize  Toxoptera  and  adults  obtained.  Fe- 
males of  Lysiphlebus  were  taken  from  Aphis  setaria  in  the  field  and 
the  issuing  parasites  in  two  cases  allowed  t<>  parasitize  Toxoptera  and 
adult-  secured.  This  experimenl  also  was  repeated  several  times. 
Female  individuals  of  Lysiphlebus  were  taken  from  the  corn  leaf- 
aphis  (Aphis  maid  is  Fitch)  in  the  field  and  the  adull  parasites  per- 
mitted to  parasitize  Toxoptera,  from  which  finally  tin-  adults  emerged. 
This  experiment  was  repeated  several  times.  Female  specimens 
Lysiphlebus   were   taken    from    the   cotton    or   melon   aphis    (Ap 

l>'i'i  ( Hov. )  from 
New  Mexico  and  given 
Toxoptera  as  a  host,  the 
adult  parasites  develop- 
ing successfully  there- 
from. Female  specimens 
of  Lysiphlebus  were 
taken  from  A/>Ii>- 
tin  hi  in  the  field  and 
given     Toxoptera    as    a      ' 

,  ,      .  i         •  Much  • ".'   i  red      (Oris  Inal.  • 

nosl .    their    onspnng 

transferred  to  .1.  maidi-radiris,  and  the  next  generation  transferred 

hack   t<>  Toxoptera.      Female  individual-  of   Lysiphlebus  were  taken 

from    I.  setaria  in  the  held  and  allowed  to  parasitize  Toxoptera,  their 

offspring  transferred  to  .  I .  s<  tai  ia .  the  next  general  ion  to  Toxoptera, 

and  the  following  generation  to  .1.  brassicce,  from  which  adults  were 

secured. 

In  many  cases  those  breedings  were  reversed.     The  only 
failure   were   in   attempting   to  transfer   Lysiphlebus   issuing    from 
Toxoptera  to  Chaitophorus  and  in  transferring  Lysiphlebus  issuing 
from  Toxoptera  to  Macrosiphum  rudbekiat.     These  experiment-  were 
reversed  with  the  same  results. 

The  female  goes  about,  if  in  grain  fields,  among  the  plant-,  and 
when  she  finds  an  aphis  she  quickly  throw-  her  abdomen  underneath 
her  body  and  between  her  legs  and  with  a  springlike  motion  thrusts 
her  ovipositor  int  i  the  body  of  the  aphis  (fig.  s>.  leaving  therein  a 

[Cir 


18 


tiny  egg.  This  egg  hatches  into  a  larva  in  a  few  days,  and  the  usual 
position  in  the  body  of  the  "green  bug"  of  the  larva  up  to  the  time 
it  becomes  full-grown  is  shown  in  fig.  6,  page  4.  Up  to  this  time  it 
has  fed  within  the  body  of  the  "green  bug"'  without  reaching  any 
of  the  vital  parts,  but  preventing  to  a  greater  or  less  degree  the 
giving  of  birth  to  young.  This  is  an  important  fact,  for,  as  the 
parasite  seems  to  prefer  partly  grown  young,  it  begins  to  check  the 
increase  of  the  pest  before  the  death  of  the  "  green  bug"  takes  place. 
Mr.  Phillips  has  found  that  females  parasitized  at  this  period  of  their 
development  do  not  reproduce  for  more  than  a  very  few  da  vs.  After 
about  six  days  the  larva  of  the  parasite  reaches  full  growth  and  becomes 
more  active,  working  its  way  about  within  the  still  living  body  of  its 

host,  which  now  dies  a  seemingly  terrible 
death.  The  motions  of  the  parasitic  larva 
within  cause  the  skin  of  the  "green  bug*' 
to  become  rotund  in  shape,  as  shown  in  fig. 
9;  the  skin  also  becomes  darker  and 
hardens.  Within  four  days  (the  life  cycle 
in  warm  weather  occupying  about  ten  day-) 
the  adult  Lysiphlebus  emerges  through  a 
round  hole  in  the  dried  skin  of  the  "  green 
bug."  as  shown  also  in  fig.  0.  In  fields 
that  have  been  destroyed  the  leave-  become 
almost  covered  by  their  brown  bodies,  as 
shown  in  fig.  7.  As  stated,  many  of  the 
"  green  bugs  "  are  stung  by  the  Lysiphlebus 
while  quite  young,  and  if  these  develop  to 
winged  adults,  as  the}'  do  at  times  in 
myriads  and  drift  away  to  distant  fields, 
they  carry  the  parasite  with  them  in  their 
bodies.  One  of  these  parasitized  winged 
females  is  shown  in  fig.  10. 

The  very  act  of  migration  of  the  "  green 
bug."  therefore,  brings  the  parasite,  and 
there  is  no  need  of  artificial  introduction,  for 
if  the  center  from  which  the  "  green  bug  "  is  migrating  has  the  para- 
sites, as  it  always  doe-,  the  latter  are  of  necessity  carried  by  their 
hosts,  and.  furthermore,  the  adult  parasites  fly  with  the  latter  with 
favoring  winds. 

During  strong  winds  the  Lysiphlebus  does  not  use  its  wings,  but 
crawls  about  over  the  plants  and  probably  does  not  become  scattered 
by  gales.  But  in  warm,  comparatively  still  weather  the  writer  has 
observed  both  winged  "  green  bugs  "  and  parasites  crawling  about  on 
the  windows  of  railway  coaches  many  miles  away  from  seriously 
infested  fields  of  grain. 
[Cir.  93] 


Fig.  0. — Dead  "  green  bugs," 
showing  hole  from  which  the 
matured  parasite  of  Lysiph- 
lebus trilici  emerges.  The 
top  figure  shows  the  lid  still 
attached,  hut  pushed  back; 
the  bottom  figure  shows  the 
parasite  emerging.  Enlarged. 
(Original,  i 


19 


EXPERIMENTS    IN    DESTROYING    "  liREEN    HIT.9       OVER    SMALL    AREAS. 


On  leaving  Washington  both  Mr.  Ainslie  and  Mr.  1'hillip-  were 
instructed  i'>  pi  ace  themselves  in  the  position  of  ;i  farmer  whose  grain 
fields  were  beginning  t<>  show  the  presence  of  the  "green  bug11  by 
small  deadening  spots,  and  to  leave  nothing  undone  or  untried  that 
would  seem  to  afford  relief  and  save  the  crop. 

Mr.  Ainslie  instituted  some  experiments  in  the  use  of  a  brush  drag 
immers,  Ark.,  and  Mr.  Phillips  carried  ou(  similar  experiments 
;.t  Hobart,  Okla.,  but  in  neither  case  was  the  measure  sufficiently 
ive  to  warrant  its  recommendation.  Experiments  in  rolling 
infested  fields  with  heavy  farm  rollers  were  conducted  by  1 »« »t  1 »  of 
these  agents,  l>m  ii  was  invariably  found  that  this  measure  was  only 
effective  on  smooth  lands.  When  the  seeding  is  done  with  a  grain 
drill,  as  most  of  ii  is,  the  plant-  gro^  up  in  the  bottoms  of  slight 
furrows,    and    the    roller   comes 


I  green 


in  contact  with  the  ridges  only. 
lca\  ing  the  young  plant-  and 
their  inhabitants  almosl  wholly 
untouched.  This  measure,  also, 
is  therefore  of  little  practical 
value. 

Mr.  Ainslie  tried  dusting  with 
lime  and  also  with  sulphur,  bul 
both  substances  were  ineffective. 

Both  Mr.  Ainslie  and  Mr.Phil 
lips  carried  out  a  series  of  care 
fill  experiment-  in  spraying  with 
kerosene  emulsion  and  with 
whale-oil  soapsuds.  From  these  experiments  it  was  found  possible 
to  destroy  50  per  cent  or  more  of  the  "green  bugs"  at  an  expense  of 
about  si  per  acre.  This  treatment,  of  course,  is  intended  for  use  only 
where,  a-  seems  to  he  more  usual  to  the  southward,  the  outbreaks  of 
the  pest  originate  in  spots  in  the  field-. 

Mr.  Ainslie  also  tried  covering  some  of  these  -pot-  with  straw  and 
burning  it.  thus  destroying,  <^'  pourse,  both  grain  and  "green  bugs." 
This,  too.  gave  encouraging  results,  and  probably  would  prove  effect- 
ive   if    applied    earlier    in    the    Season,    when    the    pe-t     first    begins    to 

appear  and  the  infested  -pot-  are  small. 

At  Hooker.  Okla..  Mr.  Phillip-  tried  th»  efficiency  of  plowing  these 
-pot-  under,  and  a-  the  field  in  which  he  was  working  was  isolated 
and  the  "green  bugs"  did  not  make  their  way  in  from  without,  he 
was  able  t<>  -how  conclusively  that  such  outbreaks,  under  certain 
condition-,  may  he  -topped. 


20 

In  summing  up  these  field  experiments,  then,  it  is  found  that  these 
spots  may  be  treated  successfully  either  by  plowing  under  and  har- 
rowing and  rolling  the  surface  of  the  ground,  by  spreading  straw 
over  them  and  burning,  or  by  treating  with  a  10  per  cent  solution  of 
kerosene  emulsion.  Except  in  the  southernmost  regions  infested  by 
this  pest,  however,  the  greatest  difficulty  does  not  arise  from  these 
i-olated  colonies,  which  seem  to  extend  outward  day  after  day.  hut 
from  the  fact  that,  after  their  food  supply  lias  become  either  largely 
destroyed  or  the  grain  too  old  and  tough  for  them  to  feed  upon, 
immense  swarms  of  winged  adults  are  produced,  and  these  drift, 
in  general,  northward  with  the  advance  of  the  season  and  infest  the 
grain  fields  of  entire  sections  of  the  country  much  earlier  and  more 
completely  than  would  he  possihle  from  the  scanty  stock  natively 
present.  This  habit  is  also  seen  in  the  behavior  of  the  pest  in  its 
original  home  in  Europe.  It  may  therefore  prove  that  the  country 
north  of  the  Red  River  may  he  more  or  less  protected  if  the  pest  can 
be  early  overcome  in  northern  Texa-. 

Agricultural  methods  of  control. 

The  fact  that  the  "  green  bug  "  in  the  South  originates  in  spots  in 
the  grain  iields  has  been  alluded  to,  and  also  that  from  these  fields 
come  the  vast  swarms  of  winged  females  that  develop  and  drift  over 
the  country,  dispersing  themselves  in  uninfected  fields.  Early  sown 
fields  or  fields  overgrown  with  volunteer  grain  seem  especially  to 
invite  early  attack  in  the  more  southern  localities.  "Where  these  im- 
mense swarms  settle  down  in  a  section  of  country,  even  the  best  field- 
ed' grain  may  succumb  to  their  attacks.  But  usually,  outside  of  an 
extremely  limited  area,  there  is  a  noticeable  difference  in  intensity  of 
attack  as  between  different  fields.  In  Oklahoma  and  northward,  fields 
that  have  been  late  sown  or  that  were  pastured  during  the  winter 
suffered  worst  and  were  the  first  to  be  destroyed.  It  has  been  fre- 
quently noticed  that  a  field  of  grain  may  be  totally  destroyed,  while 
an  adjoining  field,  though  seriously  injured,  will  frequently  pmduce 
a  partial  crop.  An  investigation  of  the  history  of  these  fields  has 
invariably  shown  that  the  result  in  the  latter  case  is  due  to  fertile  soil. 
proper  cultivation,  and  seeding  at  the  proper  time.  It  seems  to  have 
been  almost  universally  true,  outside  of  the  limited  area  of  total 
destruction,  that  the  best  farmed  fields  have  suffered  the  least.  This 
does  not  apply  alone  to  wheat,  as  the  writer  observed  a  field  of  oat- 
near  Hutchinson,  Kans.,  that  gave  promise  of  a  fair  yield,  where 
almost  the  entire  crop  would  otherwise  have  been  destroyed.  The 
owner  of  this  field,  who  had  been  obliged  to  plow  up  other  field- 
where  the  cultural  methods  had  been  the  same,  expressed  his  opinion 
[Cir.93] 


21 

thai  ili>'  reason  the  one  field  escaped  the  attack  <<\  the  "  green  bug     i" 
-i i« -I i  mi  extent  \\:i-  that  it  had  been  for  man}  years  in  alfalfa,  only 
crop,  and  that  ruin,  h.  en  taken  from  it  since  alfalfa  had 

b  ''ii  turned  under.  He  stated  that  the  "  gre  n  bug"  was  ;ii  one  time 
n-  abundant  in  this  field  as  in  the  ones  which  he  had  been  obliged  to 
plow  under,  but  that  in  the  one  case  the  plants  had  withstood  the 
attack  better  and  were  in  better  condition  when  the  "green  bugs" 
were  overcome  by  the  parasites,  and  thus  able  to  start  growth  anew 
and  \  ield  to  the  oti  ner  a  fair  percentage  <>f  n  crop. 

[n  extreme  western  Kansas  a  field  of  10  acres  of  oats  lying  adji 
to  an  irrigating  ditch,  but  which  had  not  been  irrigated,  showed  very 
forcibly  the  effect  of  irrigation.     Along  this  irrigation  ditch  wa 
ragged  border  of  vigorously  growing  oats  from  10  to  30  or  10  feet  in 
width  where  the  "green  bug"  had  seemingly  done  no  injury.     B 
yond   this,  where  the  moisture   from   the  irrigating  ditch   had   not 
penetrated,  the  loss  was  total.     In  another  case  in  the  same  locality 
a  part  of  the  wheat  in  an  unirrigated  field  came  up  in  the  fall  and  the 
not  until  spring;  the  former  was  uninjured  by  "green  bugs.'' 
while  the  latter  was  killed.     While  late  sowing  in  Texas  will  prob- 
ably lessen  attach  in  the  fall,  it   i-  doubtful   if  this  can  be  recom- 
mended north  of  the  Red   River.     November-sown   wheat    wa-  cer- 
tainly less  affected  than  others  in  North  Carolina. 

THE    PRE8EN1    "  GHEES    BUG "   -III    \  I  !"\    IN     rill:    -"l    I  ill  i:\    -I  \  1 1  -. 

m  w  1.  1909. 

The  situation  over  the  country  with  reference  to  a  future  invasion 
of  this  pest,  though  not  alarming,  i-  sufficiently  serious  to  rendei  a 
word    of   warning   exceedingly    appropriate.     In    widely    separated 
localities  from  Western  North  Carolina  to  eastern  New    Mexico  the 
insect  ha-  become  sufficiently  abundant  during  March  and  April  to 
work  considerable  injury  locally.    This  -how-  thai  the  p<-t  ha-  re- 
covered from  the  severe  reverse  given  it  by  it-  natural  enemies  in 
1907,   and    that    a    repetition   of   the   mild    winter   of    1908  9   and    the 
present  cold,  backward  spring  will  be  almost  certain  to  precipitat 
more  of  less  disastrous  invasion.     Of  course  no  one  know-  what  I 
winter  of  L909   In  and  the  spring  of  L910  will  be,  hut   it  -tan.!-  the 
grain  growers  in  hand  throughout   the  country  south  of  Virgi 
Kentucky.  Missouri,  and   Kansas  to  destroy,  a-   far  a-  p  all 

volunteer  Grain  coming  up  in  the  held-  during  the  coming  autumn: 
and  where  fall  oat-  are  sown,  a-  i-  generally  the  case  throughout  I 

Country,  the  sowing  should  he  delayed  a-  late  a-  possible.      The-.'  two 

measures  have  a  tendency  t"  prevent  the  pest  from  becomii 
oughly  established  in  the  grain  fields  during  the  autumn  months,  and 
H'ir.  ;>:;j 


22 

arc  the  only  measures  that  can  be  taken  that  will  have  a  tendency  to 
ward  off  an  impending  invasion. 

We  have  found  that  where  serious  damage  has  been  done  to  fields 
of  »rain  in  late  winter  and  spring-  such  fields  had  become  seriously 
infested  during  the  preceding  autumn.  The  carrying  out  of  these 
measures  in  the  southern  portion  of  the  country  has  a  tendency  to 
protect  the  grain  fields  farther  north,  for  we  have  had  additional 
illustration  of  the  fact  that  winged  individuals  are.  during  the  spring 
months,  being  almost  continuously  carried  northward  by  the  wind. 

It  is  somewhat  a  question  as  to  whether  the  spring-sown  oat-  far- 
ther north  would  suffer  to  a  less  degree  if  there  were  no  invasion 
in  the  South  in  fields  of  fall-sown  grain,  both  of  oats  and  wheat. 
"While  it  is  not  possible  for  an  insect  to  make  its  way  or  be  carried 
by  the  wind  from  Texas  to  northern  Kansas.  Missouri,  southern  Illi- 
nois. Indiana,  and  Ohio,  nevertheless  continuous  breedings  to  the 
southward  certainly  do  influence  the  numbers  over  this  last-mentioned 
territory. 

If  the  farmers  of  the  country,  instead  of  being  carried  away  by 
the  highly  colored  new-paper  reports  of  the  effect  of  the  introduc- 
tion of  a  few  parasites  in  their  fields,  will  seek  to  evade  the  pest  by 
the  destruction  of  volunteer  grain  in  the  fall  and  late  sowing  in  the 
extreme  South  and  turn  their  attention  to  better  farm  methods,  in- 
cluding not  only  cultural  methods  but  by  all  means  rotation  of  crop-, 
watching  for  and  stamping  out  the  pest  when  it  first  appears  in  the 
South  in  the  fall  and  winter,  they  will  in  all  probability  suffer  far 
les>  from  destruction  of  their  ci'ops  when  the  next  invasion  of  this 
pest  occurs. 

Approved : 

James  "Wilson, 

Secretary  of  Agricultun  . 

Washington,  D.  C,  April  27,  1909. 

[Cir.  93] 

O 


UNIVERSITY  OF  FLORIDA 


3  1262  09216  4465 


